Loud speaker device



Mrch 12, 1935. Q w o 2 1,994,297

LOUD SPEAKER DEVICE Filed July 31, 1930 Patented Mar. 12, 1935 UNlTiEDSTATES PATENT OFFICE Application July 31, 1930, Serial N11. 472,074In'Germany August 7, 1929 '4 Claims. (Cl. 179 4) This :invention relatesto a loudspeaker system which is characterized by the arrangement of afreely oscillatable multiple armed armature rotatable around a pivotaxle. Y 1 V 5 Such loudspeaker systems are known, wherein, for example,the coils conducting the alternating current are fitted on'the poles oron the armature. The objection of such a construction is chiefly thatthe armature system does not pass out of the field range of the magnetsand also cannot move at right angles to the magnetic lines of force; thearmature'likewise does not always automatically come into itsinoperative position without external additional forces. Moreover, thefitting of the known systems is complicated and has too large masses.All these properties exert adetrimental influence on the soundproduction as regards timbre and volume of sound.

The invention avoids these objections substantially in that the armatureconsists of arms distributed like wheel spokes around the common pivotaxle and arranged with a small air gap between the middle andedgesurfaces of two coaxial pot-shaped pole pieces each connected to anarm of a permanent horse-shoe magnet. The middle and edge surfaces ofthese pole pieces are so constructed that a number of. tooth-likeprojecting poles corresponding to the number of armature arms areproduced, the teeth opposite one another in the middle and edge zones ofthe two pole pieces being, however, mutually displaced so that a toothof the middle zone on one side is covered by its coordinate armaturearm, whereas the corresponding tooth of the outer zone is covered fromthe other side by the armature arm, and coils leading the talkingcurrent are accommodated one in each of the free spaces of thepot-shaped pole pieces coaxially 40 to the armature in the pole pieces.The control is effected in such a manner that, according to thedirection of the alternating flux the force flux produced by thepermanent magnet is amplified at the middle surface of the pot-shapedpole pieces and at the same time attenuated at the outer surfaces orinversely, so that the armature performs rotary movements in onedirection or the other and when no alternating current is flowingreturns into its medial position under the action of thepermanentattraction. v I

The tooth-shaped projecting poles of the middle and edge surfaces bothof the pot-shaped poles and also of the two differently polarized poleshoe pieces are opposite and their coordinate armature arms are so bentthat in position of rest they cover on one side the tooth-shapedprojecting poles of the middle pole surfaces, and on the other side thetooth-shaped projecting poles of the edge surfaces.

An embodiment of the invention is illustrated by way of example in theaccompanying drawing in which:

Figure 1 is a longitudinal section showing a loud-speaker system withpermanent horse-shoe magnet with coils arranged between its arms;

Figure 2 is a top plan view of Figure 1, with one arm of the magnetremoved;

Figure 3 is a perspective view of the magnet system.

The armature is composed of radial arms a rotatable around a common axleand mounted between two pot-shaped pole pieces connected by a ring e andarranged between the two arms of a horse-shoe magnet g. The twopot-shaped pole pieces have tooth-like projections 0 near their middleportion and similar projections 12 near their periphery. These middleand circumferential projections are mutually displaced so that thearmature arms a only cover the projections b from one side and theprojections c from the other side. Coils d are arranged in the space ofeach of the pot-shaped pole pieces coaxially to the armature a and areconnected in such a manner that according to the direction of thealternating flux the force flux emanating from the permanent magnet g isamplified at the middle of the pot-shaped pole pieces and at the sametime attenuated at the circumference of the pole pieces or inversely,causing the armature a. to rotate. The movement of the armature istransmitted in known manner to the diaphragm connected to the mouthpiecei of the loudspeaker.

I claim:---" 7 1. A loudspeaker system, comprising in combination ahorseshoe magnet, an armature freely rotatable between the arms of saidmagnet and having a plurality of, radially projecting spoke like arms,two coaxial pot shaped pole pieces, one connected with each arm of saidmagnet and surrounding said armature, toothshaped poles projecting fromthe middle and edges of the inner .side of both of said pole piecescorresponding in number to the number of armature arms and forming asmall air gap. between the ends and middle portions of said armaturearms, said poles being mutually displaced so that a toothin the middlezone is covered by its coordinate armature arm on one side, whereas thecorresponding tooth in the outer zone is covered from the other side,and

coils, one within the free space in each of said pole pieces coaxialwith said armature, so connected that according to the direction of thealternating flux the force flux emanating said permanent magnet isamplified at the middle of said pot-shaped pole pieces and at the sametime attenuated at the outer portion of saidpole pieces or inversely, sothat said armature is rotated in one or other direction and is returnedinto its central position under the permanent attraction of said magnetwhen no alternating current flows through said coils.

2. A loudspeaker system, comprising in combination, a horse shoe magnet,an armaturefreely rotatable between the arms of said magnet and having aplurality ofradially projecting spoke-like arms and two coaxial potshaped pole pieces, one connected with each arm of said magnet andsurrounding said armature 3, A loudspeaker system, comprising incombination, a horse shoe magnet, an armature freely rotatable betweenthe arms of said magnet and having a plurality of radially projectingspoke-like arms and two coaxial pot shaped pole pieces, one connectedwith each arm of said magnet and surrounding said armature, tooth shapedpoles projecting from the middle and edges of the inner sides ofboth ofsaid pole pieces corresponding in number to the number of armature armsand forming a small air gap 1 between theends and middle portions ofsaid armature arms.

4. A loudspeaker system, comprising in combination, a horse shoemagnet,-.an armature freely rotatable between thearms of said magnet andhaving a plurality of radially projecting spoke-like arms andtwo coaxialpot shaped pole pieces, one connected with each arm of said magnet andsurrounding said armature, tooth shaped poles vprojecting from themiddle and edges of the inner sides of both of sai'd'pole piecescorresponding in number to the number of armature arms and forming asmall air gap between the ends and middle portions of said armaturearms, said poles being mutually displaced, so that a tooth in the middlezone is covered by itscoordinate armature arm on one side,

whereas the corresponding toothin the outer zone is covered from theother side.

r HANS WITTORF.

